1. Technical Field of the Invention
The present invention is related to a flicker detection apparatus, a flicker correction apparatus, an image-pickup apparatus, a flicker detection program and a flicker correction program. In particular, it can be applied preferably to an image-pickup apparatus which implements exposure control via a focal plane shutter system.
2. Background Technology and Problems to be Solved by the Invention
In a conventional image-pickup apparatus, an image is picked up by shutter operation for each line by using a device like a CMOS sensor and using an exposure method similar to a focal plane shutter system.
However, in an image-pickup apparatus using an exposure method similar to a focal plane shutter system, there is a problem that lateral stripes occur in an image depending on specific shutter time, when an image is picked up with a flicker light source. Namely, shutter timing is different for every line in an image-pickup apparatus using an exposure method similar to a focal plane shutter system. Further, in a flicker light source, brightness fluctuates by a specific period.
Hence, on the line where the shutter is released at the time of high brightness of a flicker light source, a lot of electric charge is accumulated so that the image pixel of the line has higher brightness. On the other hand, on the line where the shutter is released at the time of low brightness of a flicker light source, a low electric charge is accumulated so that the image pixel of the line has low brightness. As a result, in an image picked up under a flicker light source, brightness of each line fluctuates periodically so that lateral stripes occur in an image. Therefore, when a subject having uniform brightness is picked up under a flicker light source, the occurrence of flicker is easily detected by observing lateral stripes that appear in an image.
On the other hand, in the case of picking up an image of normal scenery under a flicker light source, it is difficult to determine a case when lateral stripes occur due to the affect of flicker, or a case when such stripes occur due to a difference of high brightness on the scenery itself, if lateral stripes which appear are observed. Hence, in the conventional method, it is difficult to detect the occurrence of flicker in a case when a subject such as scenery or a person is picked up normally.
Therefore, an object of the present invention is to provide a flicker detection apparatus, a flicker correction apparatus, an image-pickup apparatus, a flicker detection program and a flicker correction program that can improve the accuracy of detecting flicker at the time of picking up a subject normally.